A variety of coating compositions have been reported for several decades. More recently, however, advances in fabrication and characterization methods of nanostructured films have helped spark renewed interest of these films for use in a wide range of applications. The drive for ever smaller feature sizes in coatings and substrates has been brought about through a desire to achieve attractive properties for applications in, for example, micro-electronics, anti-reflective coatings for displays and super-hydrophobic, and even self-cleaning surfaces.
The electronics industry utilizes such materials as insulating layers between circuits and components of integrated circuits and associated electronic devices with the aim of increasing speed and storage capability of microelectronic devices (e.g., computer chips). On the other hand antireflection coatings are generally disposed on an outermost surface of an image display device such as polarizing film for a liquid crystal display (LCD), the front plate of a touch panel (PET substrate), the front plate of a projection television (PC substrate), the front plate of a cathode ray tube display or plasma display panel (glass substrate), or an optical lens, to reduce reflectance and prevent optical interference or image glare caused by external light and enhance the visibility of image.
A number of fabrication methods are described. U.S. Pat. No. 5,895,263 describes forming a nanoporous silica dielectric film on a substrate, e.g., a wafer, by applying a composition comprising decomposable polymer and organic polysilica, i.e., including condensed or polymerized silicon polymer, heating the composition to further condense the polysilica, and decomposing the decomposable polymer to form a porous dielectric layer. This process, like many of the previously employed methods of forming nanoporous films on semiconductors, has the disadvantage of requiring heating for both the aging or condensing process, and for the removal of a polymer to form the nanoporous film. Furthermore, there is a disadvantage that organic polysilica tends to increase in molecular weight after the solution is prepared; consequently, the viscosity of such precursor solutions increases during storage, and the thickness of films made from stored solutions will increase as the age of the solution increases. The instability of organic polysilica thus requires short shelf life, cold storage, and fine tuning of the coating parameters to achieve consistent film properties in a microelectronics/integrated circuit manufacturing process.
There is a present need and current demand for new and improved coatings and compatible substrates that can be applied to a variety of applications, including the examples recited above of electronic devices and antireflection applications This is coupled with a continuing desire to reduce the cost in time, money and manufacturing equipment of producing such polymer composites and devices coated therewith. There remains this ongoing need for further improvements in both the desirable properties of nanoporous coatings, as well as an ongoing need for further improvements in methods for producing such coatings and complementary substrates.